Topic
Urea
About: Urea is a research topic. Over the lifetime, 21394 publications have been published within this topic receiving 382444 citations. The topic is also known as: carbamide & carbonic acid diamide.
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TL;DR: It is concluded that the fall in plasma glucose concentration is primarily caused by renal glucose excretion, and that the absence of a maximal renal tubular reab-sorption rate for either acetoacetate (AcAc) or beta-hydroxybutyrate (β-OHB) serves to mitigate urinary losses of sodium and potassium during diabetic ketoacidosis.
Abstract: Although diabetic ketoacidosis is characterized by increased renal excretion of glucose, ketone bodies, and nitrogenous compounds, there are few quantitative studies pertaining to renal function during this state. Therefore, renal function was studied in 10 adult patients in moderate to severe diabetic ketoacidosis before insulin administration. Admission plasma concentrations were: glucose 21.4 (9.2–39.4) mM or 386 (166–710) mg/dl, acetoacetate 3.0 (1.3–7.4) mM, beta-hydroxybutyrate 7.9 (2.9–15.2) mM, acetone 4.4 (1.3–8.9) mM, and HCO3 12.8 (9.5–17.8) mM. Arterial blood pH was 7.28 (7.21–7.38). Partial rehydration was achieved with 0.45% saline. Inulin was used to measure GFR. Renal clearance of acetoacetate, beta-hydroxybutyrate, acetone, glucose, and urinary excretion of nitrogenous compounds were determined.
Partial rehydration reduced plasma glucose concentration, primarily because of renal excretion, amounting to 384 ± 73 μmol/min or 69 ± 13 mg/min. Partial rehydration had no effect on plasma ketone bodies, on bicarbonate or urea concentrations, or on arterial pH. Partial rehydration had no effect on ketone body or nitrogenous compound excretory rates.
Reabsorptive rates of acetoacetate, beta-hydroxybutyrate, acetone, and glucose increased linearly with their filtered loads, and no maximal renal tubular transport rates were demonstrated for any ketone body or glucose. Because renal absorption of ketone bodies was less than 100%, ketonuria increased as filtered loads increase. Unlike ketone bodies, glucose reabsorptive rate was directly related to GFR.
Total renal excretion of nitrogen in the forms of urea, ammonium, creatinine, and uric acid amounted to 16 ± 2 mg/min. This huge loss of body nitrogen reflected ongoing protein catabolism and not heightened renal excretion of preformed compounds, as the plasma concentrations of urea, creatinine, and uric acid did not change during the study. Urea nitrogen accounted for 12 ± 2 mg/min (72%) of the total nitrogen excreted. Ammonium excretion was markedly augmented, ranging from 76 to 537 μmol/min, and was inversely related to arterial pH.
We conclude that the fall in plasma glucose concentration is primarily caused by renal glucose excretion, and that the absence of a maximal renal tubular reab-sorption rate for either acetoacetate (AcAc) or beta-hydroxybutyrate ( β -OHB) serves to mitigate urinary losses of sodium and potassium during diabetic ketoacidosis.
84 citations
TL;DR: Experimental and theoretical spectroscopic results and simulations show that water's rotational dynamics are slowed down by urea, consistent with the idea that urea only very weakly perturbs the water structure.
Abstract: Urea/water is an archetypical “biological” mixture and is especially well-known for its relevance to protein thermodynamics as urea acts as a protein denaturant at high concentration. This behavior has given rise to an extended debate concerning urea’s influence on water structure. On the basis of a variety of methods and of definitions of the water structure, urea has been variously described as a structure-breaker, a structure-maker, or as remarkably neutral toward water. Because of its sensitivity to microscopic structure and dynamics, vibrational spectroscopy can help resolve these debates. We report experimental and theoretical spectroscopic results for the OD stretch of HOD/H2O/urea mixtures (linear IR, 2DIR, and pump–probe anisotropy decay) and for the CO stretch of urea-D4/D2O mixtures (linear IR only). Theoretical results are obtained using existing approaches for water and a modification of a frequency map developed for acetamide. All absorption spectra are remarkably insensitive to urea concent...
84 citations
TL;DR: Findings from this work indicated that bio-based PU derived from sawdust can be used as coating materials for PCU, particularly after EP modification, and the resulting EMPCU was more environmentally friendly and cost-effective than conventional urea fertilizers coated by EP.
Abstract: A novel polymer-coated nitrogen (N) fertilizer was developed using bio-based polyurethane (PU) derived from liquefied locust sawdust as the coating material. The bio-based PU was successfully coated on the surface of the urea fertilizer prills to form polymer-coated urea (PCU) fertilizer for controlled N release. Epoxy resin (EP) was also used to further modify the bio-based PU to synthesize the interpenetrating network (IPN), enhancing the slow-release properties of the PCU. The N release characteristics of the EP-modified PCU (EMPCU) in water were determine at 25 °C and compared to that of PCU and EP-coated urea (ECU). The results showed that the EP modification reduced the N release rate and increased the longevity of the fertilizer coated with bio-based PU. A corn growth study was conducted to further evaluate the filed application of the EMPCU. In comparison to commercial PCU and conventional urea fertilizer, EMPCU was more effective and increased the yield and total dry matter accumulation of the co...
84 citations
TL;DR: Embryological development of the urea cycle in the tadpole and in mammalian fetal liver therefore permits use of amino acids as new sources of energy to meet oxidative demands for continuing growth.
84 citations
83 citations